JAZZACE  PTHPasteboard (lite version) has been very useful these past few months, but I am glad I didn't buy the pro version. Their web site has been reduced to the notice:

PTHPasteboard is no longer available for sale because of Snow Leopard issues.

You can still download it here.

So it looks like the end is nigh.  
(Version 4.4.1)

JAZZACE  I've been waiting for this widget for a long time, as the provider is the cable weather channel in Canada. For that reason, it is better and more knowledgeable about Canadian addresses, and even offers the choice of English or French. The back of the widget gives quick links to other parts of their web site. The only issue I occasionally have with it is how it deals with the forecast for today. At a certain point in the day, it determines that you don't need to know about today. That point happens too early for my taste, but that is more of a data feed issue than a design issue. I would love to see them add a widget for their hourly forecasts; that would be unique and useful! Nevertheless, a useful widget.  
(Version 1.0)